Plotting method and device



s. G. GAMBLE PLoTTING METHOD ANDl DEVICE April 27, 1954 Filed Feb. 14. 1952 Patented Apr. 27, 1954v PLOTTIN G METHOD ND `DEVIE Ottawa, Ontario, Canada, esty the King in the right of Canada, as represented 4l'iy the Minister' of Mines and Technical Surveys Application February 14, 1952, serial No`.`2"z1,565 f Y Samuel Gill Gamble,

assignor to His Maj 'Ihis invention relates to the art of plotting topographical maps and plans from aerial photographs having stereoscopic overlaps. p

In the art of preparing topographical maps, itis common practice to project upon a mapping surface a stereoscopic image from a pair of aerial photographs.` It is also common practice to employ in association with such image index meanssupported on the mapping surface and having` a luminous mark by means of whichany particular plane in the terrain of the image may be established and the contour thereof traced upon the mapping surface.

It is an object of the present invention to provide a method and means for producing a broad visually transparent plane adjustable to intersect a three dimensional optically projected image at any desired elevation and having thereon a multiplicity of luminous targets in or on the surface of the plane whereby the operator can estimate the position of the plane over the whole surface of the image intersected by the plane. A further object is to produce such a plane on the surface of which the projected images are actually resolved. ,Y

y ,The invention will be to the accompanying drawing in which Figure 1 is vanisometric view of the tracing table of the present invention in associationV with conventional mapping equipment,

Figure 2 is an enlarged isometric view of the tracing table with parts broken away,

Figure 3 is an enlarged side elevation of the tracing table in slightly modified form, and

Figure 4 is an enlarged sectional view of still another modified portion of the tracing table.

In the drawing, I is a mapping stand having a mapping table 2 and a pair of projectors 3 suspended over the table for projection of the stereoscopic image in the usual manner.

The tracing table of the present invention is indicated generally at Il and comprises a rectangular boxlike frame 5 having mounted therein described with referenceV 7' claims. (01. 33 1) illuminating means 6 and a iiat top member 1V which is generally opaque but which is provided with a multiplicity of very small pin holes or perforations 8 for passage of light therethrough and adapted to constitute the targets of the present invention. The holes or perforations 8 are shown as of exaggerated size in Figs. 2, 3 and 4 of the drawings, and eachY will normally not be substantially larger than approximately 0.004" in diameter. The holes should occur at intervals not substantially exceeding 0.30 inch throughout the member '1. The size of member Y. Z 'inlay vary within wide limits but 30 inches long by 15 inches` wide has been found to provide a satisfactory working surface.

Themember 'l may be formed in various Ways.

As shown in Figure 2, it comprises a glass plate 9 surmounted by an opaque sheet I0 of paper or like -material, thev holes 8 being formed in the' sheet I0. As shown in Figure 3, it may comprise a metal plate I|,` having a layei I 2L oi opaque' white paint on its upper surface, the holes 8 extending through the plate and layer. As shown in Fig.' 4 it may comprise a glass plate I3 having a layer I d'of opaque white paint'on its upper surface, the holes 8 being' etched through the paint layer I4.

' The illuminating means E is such as to provide substantially uniform illumination of the under surface of member 1 for production of targets of generally uniform luminosity. As shown, the means may comprise a ybattery of luniformly spaced electric lamps I5 connected to any suit-- able source of power by wires I6 through a conventional switch I1 mounted on frame 5. Means such as a transformer I8 having a control knob I9, are preferably provided for adjusting the intensity of the illumination provided bythe lamps.

The frame 5 is mounted on any suitable supporting means which isadjustable to vary the height and inclination ofthe frame and member 'I witlfrrespectV to'thev mapping table 2 on which it is-adaptedtobe supported. As shown, such means may comprise three legs 20, two at the forward portion of the table and one at the rearward portion. Each leg 20 may comprise a post 2|, a sleeve 22 on the post and fixed to the frame 5, and a knurled nut 23 on a lower screwthreaded -portion 24 of the post and rotatable to move the sleeve frame in a perpendicular direction. Preferably, a set screw 25 is provided in the sleeve for locking engagement with the post. For wide adjustment, the set screw may be loosened and the frame moved up or down manually, the knurled nut 23 being employed for fine adjustments. An indicating scale 26 may be mounted on each post for accuracy of adjustment.

As shown in Figure 3, the electric lamps I5 may be mounted on a separate tray 21 slidably mounted in frame 5 for ease of replacement of the lamps.

Means for producing a iiow of cooling air through the frame 5 may comprise an opening 28 in the front wall of the frame and a conduit 29 connected to the rear wall of the frame, as shown.

tensity to produce areadily visible p lane grid` of such targets on the intersecting the image.

drawingA material and` After any necessary adjustment of the member 1 as to inclination to compensate for corresponding inclination in the basic photographs from which theimageisprcduced, the member 1 is adjusted ma perpendicular direction until the luminous grid intersects the three-dimensional imagdesired plane in the terrain thereof. Thereafter the ccntoury of the terrain at such plane is traced directly upon the drawing material' using anynoi-mal; marking device.

It will be observed that, since the mapping material issuperimposed onthepdevice, the operator has an entirely unobstructed'view ofythetopography he is mapping. Moreover, the o perator employs directly any normal marking de vice, such as apen erA pencil; for delineating detail on the mappingsurface. Therefore, the operator may see what he haspreviously drawn, and thus avoid inconsistencies in the drawing. Errorsin the drawing arealso readily detectable and corrected.

The,l device is subject is v convenient land iner-` pensive manufactureandmayf be employed with` standard types of mapp" 'g equipment.

What isclaimed is:

l. A method of plotting topographical informa@ tionV which` includes the step; o projecting a stereoscopic image from` a stereoscopic pair of images `and which comprises'.I placing in a `common plane a mltiplieityof visible targets at frequent intervals extending over an area rat, least' as great as that ci the major. portion of said image, locating sa'idccrnrnon plane targets in intersecting relation vtosaid ster'eoscfsopi'z.A image, and plotting detail fromfsaid stereoscopic vimage directly upon 'mapping material `lz'xvzate'd in `said commonplane.. n l l e 1 2. Av topographical plotting., devicer comprising a frame, a flat top,rneinhermounted in the frame, lighting devices mounted in ythe irame below said member. andY being; uniiormlr arranged t0 ri- Vid Substantially *uniQlmV-dfsbributon 0f 1181112.

1 in claim `2,4 saidl fiat upon the lower surface of said member, means for varying the intensity of the light provided by said devices, said member having a multiplicity of pin holes therein for passage therethrough of light from said devices and being otherwise substantially opaque, and legs supporting said frame, at least` one of said legsbeing-'adjustable as to height to vary the inclination and' height of `said member.

3. A topographical plotting device as denecl in claim 2; saidflat top member comprising a glassplate having a layer of opaque paint thereon, saidholes being etched in said paint.

4;.,Atopographical plotting device as dened l top member comprising a glass plate, and a sheet of opaque material superimposed on said plate, said holes being formed in said sheet.

5'.' A topographical plotting device comprising a, frame, a flat top member mounted in the frame, a-fplur'ality of'` electrical lighting devices mounted in the-frame below saidrnember. said devices being uniformly arranged to provide substanv tially uniform distribution of ylight upon the lower surface of said member, means for varying the intensity of the light provided'by said devices, said member having a multiplicity of pin holes therein for passage therethrough of light from said devices and being otherwise supporting legs fixed to said frame, each saidleg being adjustable as to height tovary theV in clination and heightof i said i member.

6. A topographical plotting device as deiinedl in vcla-im 5, said holes being spaced apart not 1 substantially more than approximately 0.130 inch.

7'. A topographical vplotting devicefas 'defined in claim 5, each said hole havinga diameter'not substantially exceeding 0.004 inch.

Opaque, and 

